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<pre><span class="sourceLineNo">001</span>/*<a name="line.1"></a>
<span class="sourceLineNo">002</span> * Copyright (C) 2010 The Guava Authors<a name="line.2"></a>
<span class="sourceLineNo">003</span> *<a name="line.3"></a>
<span class="sourceLineNo">004</span> * Licensed under the Apache License, Version 2.0 (the "License");<a name="line.4"></a>
<span class="sourceLineNo">005</span> * you may not use this file except in compliance with the License.<a name="line.5"></a>
<span class="sourceLineNo">006</span> * You may obtain a copy of the License at<a name="line.6"></a>
<span class="sourceLineNo">007</span> *<a name="line.7"></a>
<span class="sourceLineNo">008</span> * http://www.apache.org/licenses/LICENSE-2.0<a name="line.8"></a>
<span class="sourceLineNo">009</span> *<a name="line.9"></a>
<span class="sourceLineNo">010</span> * Unless required by applicable law or agreed to in writing, software<a name="line.10"></a>
<span class="sourceLineNo">011</span> * distributed under the License is distributed on an "AS IS" BASIS,<a name="line.11"></a>
<span class="sourceLineNo">012</span> * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.<a name="line.12"></a>
<span class="sourceLineNo">013</span> * See the License for the specific language governing permissions and<a name="line.13"></a>
<span class="sourceLineNo">014</span> * limitations under the License.<a name="line.14"></a>
<span class="sourceLineNo">015</span> */<a name="line.15"></a>
<span class="sourceLineNo">016</span><a name="line.16"></a>
<span class="sourceLineNo">017</span>package com.google.common.collect;<a name="line.17"></a>
<span class="sourceLineNo">018</span><a name="line.18"></a>
<span class="sourceLineNo">019</span>import static com.google.common.base.Preconditions.checkArgument;<a name="line.19"></a>
<span class="sourceLineNo">020</span>import static com.google.common.base.Preconditions.checkNotNull;<a name="line.20"></a>
<span class="sourceLineNo">021</span>import static com.google.common.base.Preconditions.checkPositionIndex;<a name="line.21"></a>
<span class="sourceLineNo">022</span>import static com.google.common.base.Preconditions.checkState;<a name="line.22"></a>
<span class="sourceLineNo">023</span><a name="line.23"></a>
<span class="sourceLineNo">024</span>import com.google.common.annotations.Beta;<a name="line.24"></a>
<span class="sourceLineNo">025</span>import com.google.common.annotations.VisibleForTesting;<a name="line.25"></a>
<span class="sourceLineNo">026</span>import com.google.common.math.IntMath;<a name="line.26"></a>
<span class="sourceLineNo">027</span><a name="line.27"></a>
<span class="sourceLineNo">028</span>import java.util.AbstractQueue;<a name="line.28"></a>
<span class="sourceLineNo">029</span>import java.util.ArrayDeque;<a name="line.29"></a>
<span class="sourceLineNo">030</span>import java.util.ArrayList;<a name="line.30"></a>
<span class="sourceLineNo">031</span>import java.util.Collection;<a name="line.31"></a>
<span class="sourceLineNo">032</span>import java.util.Collections;<a name="line.32"></a>
<span class="sourceLineNo">033</span>import java.util.Comparator;<a name="line.33"></a>
<span class="sourceLineNo">034</span>import java.util.ConcurrentModificationException;<a name="line.34"></a>
<span class="sourceLineNo">035</span>import java.util.Iterator;<a name="line.35"></a>
<span class="sourceLineNo">036</span>import java.util.List;<a name="line.36"></a>
<span class="sourceLineNo">037</span>import java.util.NoSuchElementException;<a name="line.37"></a>
<span class="sourceLineNo">038</span>import java.util.PriorityQueue;<a name="line.38"></a>
<span class="sourceLineNo">039</span>import java.util.Queue;<a name="line.39"></a>
<span class="sourceLineNo">040</span><a name="line.40"></a>
<span class="sourceLineNo">041</span>/**<a name="line.41"></a>
<span class="sourceLineNo">042</span> * A double-ended priority queue, which provides constant-time access to both<a name="line.42"></a>
<span class="sourceLineNo">043</span> * its least element and its greatest element, as determined by the queue's<a name="line.43"></a>
<span class="sourceLineNo">044</span> * specified comparator. If no comparator is given at construction time, the<a name="line.44"></a>
<span class="sourceLineNo">045</span> * natural order of elements is used.<a name="line.45"></a>
<span class="sourceLineNo">046</span> *<a name="line.46"></a>
<span class="sourceLineNo">047</span> * &lt;p&gt;As a {@link Queue} it functions exactly as a {@link PriorityQueue}: its<a name="line.47"></a>
<span class="sourceLineNo">048</span> * head element -- the implicit target of the methods {@link #peek()}, {@link<a name="line.48"></a>
<span class="sourceLineNo">049</span> * #poll()} and {@link #remove()} -- is defined as the &lt;i&gt;least&lt;/i&gt; element in<a name="line.49"></a>
<span class="sourceLineNo">050</span> * the queue according to the queue's comparator. But unlike a regular priority<a name="line.50"></a>
<span class="sourceLineNo">051</span> * queue, the methods {@link #peekLast}, {@link #pollLast} and<a name="line.51"></a>
<span class="sourceLineNo">052</span> * {@link #removeLast} are also provided, to act on the &lt;i&gt;greatest&lt;/i&gt; element<a name="line.52"></a>
<span class="sourceLineNo">053</span> * in the queue instead.<a name="line.53"></a>
<span class="sourceLineNo">054</span> *<a name="line.54"></a>
<span class="sourceLineNo">055</span> * &lt;p&gt;A min-max priority queue can be configured with a maximum size. If so,<a name="line.55"></a>
<span class="sourceLineNo">056</span> * each time the size of the queue exceeds that value, the queue automatically<a name="line.56"></a>
<span class="sourceLineNo">057</span> * removes its greatest element according to its comparator (which might be the<a name="line.57"></a>
<span class="sourceLineNo">058</span> * element that was just added). This is different from conventional bounded<a name="line.58"></a>
<span class="sourceLineNo">059</span> * queues, which either block or reject new elements when full.<a name="line.59"></a>
<span class="sourceLineNo">060</span> *<a name="line.60"></a>
<span class="sourceLineNo">061</span> * &lt;p&gt;This implementation is based on the<a name="line.61"></a>
<span class="sourceLineNo">062</span> * &lt;a href="http://portal.acm.org/citation.cfm?id=6621"&gt;min-max heap&lt;/a&gt;<a name="line.62"></a>
<span class="sourceLineNo">063</span> * developed by Atkinson, et al. Unlike many other double-ended priority queues,<a name="line.63"></a>
<span class="sourceLineNo">064</span> * it stores elements in a single array, as compact as the traditional heap data<a name="line.64"></a>
<span class="sourceLineNo">065</span> * structure used in {@link PriorityQueue}.<a name="line.65"></a>
<span class="sourceLineNo">066</span> *<a name="line.66"></a>
<span class="sourceLineNo">067</span> * &lt;p&gt;This class is not thread-safe, and does not accept null elements.<a name="line.67"></a>
<span class="sourceLineNo">068</span> *<a name="line.68"></a>
<span class="sourceLineNo">069</span> * &lt;p&gt;&lt;i&gt;Performance notes:&lt;/i&gt;<a name="line.69"></a>
<span class="sourceLineNo">070</span> *<a name="line.70"></a>
<span class="sourceLineNo">071</span> * &lt;ul&gt;<a name="line.71"></a>
<span class="sourceLineNo">072</span> * &lt;li&gt;The retrieval operations {@link #peek}, {@link #peekFirst}, {@link<a name="line.72"></a>
<span class="sourceLineNo">073</span> *     #peekLast}, {@link #element}, and {@link #size} are constant-time<a name="line.73"></a>
<span class="sourceLineNo">074</span> * &lt;li&gt;The enqueing and dequeing operations ({@link #offer}, {@link #add}, and<a name="line.74"></a>
<span class="sourceLineNo">075</span> *     all the forms of {@link #poll} and {@link #remove()}) run in {@code<a name="line.75"></a>
<span class="sourceLineNo">076</span> *     O(log n) time}<a name="line.76"></a>
<span class="sourceLineNo">077</span> * &lt;li&gt;The {@link #remove(Object)} and {@link #contains} operations require<a name="line.77"></a>
<span class="sourceLineNo">078</span> *     linear ({@code O(n)}) time<a name="line.78"></a>
<span class="sourceLineNo">079</span> * &lt;li&gt;If you only access one end of the queue, and don't use a maximum size,<a name="line.79"></a>
<span class="sourceLineNo">080</span> *     this class is functionally equivalent to {@link PriorityQueue}, but<a name="line.80"></a>
<span class="sourceLineNo">081</span> *     significantly slower.<a name="line.81"></a>
<span class="sourceLineNo">082</span> * &lt;/ul&gt;<a name="line.82"></a>
<span class="sourceLineNo">083</span> *<a name="line.83"></a>
<span class="sourceLineNo">084</span> * @author Sverre Sundsdal<a name="line.84"></a>
<span class="sourceLineNo">085</span> * @author Torbjorn Gannholm<a name="line.85"></a>
<span class="sourceLineNo">086</span> * @since 8.0<a name="line.86"></a>
<span class="sourceLineNo">087</span> */<a name="line.87"></a>
<span class="sourceLineNo">088</span>// TODO(kevinb): GWT compatibility<a name="line.88"></a>
<span class="sourceLineNo">089</span>@Beta<a name="line.89"></a>
<span class="sourceLineNo">090</span>public final class MinMaxPriorityQueue&lt;E&gt; extends AbstractQueue&lt;E&gt; {<a name="line.90"></a>
<span class="sourceLineNo">091</span><a name="line.91"></a>
<span class="sourceLineNo">092</span>  /**<a name="line.92"></a>
<span class="sourceLineNo">093</span>   * Creates a new min-max priority queue with default settings: natural order,<a name="line.93"></a>
<span class="sourceLineNo">094</span>   * no maximum size, no initial contents, and an initial expected size of 11.<a name="line.94"></a>
<span class="sourceLineNo">095</span>   */<a name="line.95"></a>
<span class="sourceLineNo">096</span>  public static &lt;E extends Comparable&lt;E&gt;&gt; MinMaxPriorityQueue&lt;E&gt; create() {<a name="line.96"></a>
<span class="sourceLineNo">097</span>    return new Builder&lt;Comparable&gt;(Ordering.natural()).create();<a name="line.97"></a>
<span class="sourceLineNo">098</span>  }<a name="line.98"></a>
<span class="sourceLineNo">099</span><a name="line.99"></a>
<span class="sourceLineNo">100</span>  /**<a name="line.100"></a>
<span class="sourceLineNo">101</span>   * Creates a new min-max priority queue using natural order, no maximum size,<a name="line.101"></a>
<span class="sourceLineNo">102</span>   * and initially containing the given elements.<a name="line.102"></a>
<span class="sourceLineNo">103</span>   */<a name="line.103"></a>
<span class="sourceLineNo">104</span>  public static &lt;E extends Comparable&lt;E&gt;&gt; MinMaxPriorityQueue&lt;E&gt; create(<a name="line.104"></a>
<span class="sourceLineNo">105</span>      Iterable&lt;? extends E&gt; initialContents) {<a name="line.105"></a>
<span class="sourceLineNo">106</span>    return new Builder&lt;E&gt;(Ordering.&lt;E&gt;natural()).create(initialContents);<a name="line.106"></a>
<span class="sourceLineNo">107</span>  }<a name="line.107"></a>
<span class="sourceLineNo">108</span><a name="line.108"></a>
<span class="sourceLineNo">109</span>  /**<a name="line.109"></a>
<span class="sourceLineNo">110</span>   * Creates and returns a new builder, configured to build {@code<a name="line.110"></a>
<span class="sourceLineNo">111</span>   * MinMaxPriorityQueue} instances that use {@code comparator} to determine the<a name="line.111"></a>
<span class="sourceLineNo">112</span>   * least and greatest elements.<a name="line.112"></a>
<span class="sourceLineNo">113</span>   */<a name="line.113"></a>
<span class="sourceLineNo">114</span>  public static &lt;B&gt; Builder&lt;B&gt; orderedBy(Comparator&lt;B&gt; comparator) {<a name="line.114"></a>
<span class="sourceLineNo">115</span>    return new Builder&lt;B&gt;(comparator);<a name="line.115"></a>
<span class="sourceLineNo">116</span>  }<a name="line.116"></a>
<span class="sourceLineNo">117</span><a name="line.117"></a>
<span class="sourceLineNo">118</span>  /**<a name="line.118"></a>
<span class="sourceLineNo">119</span>   * Creates and returns a new builder, configured to build {@code<a name="line.119"></a>
<span class="sourceLineNo">120</span>   * MinMaxPriorityQueue} instances sized appropriately to hold {@code<a name="line.120"></a>
<span class="sourceLineNo">121</span>   * expectedSize} elements.<a name="line.121"></a>
<span class="sourceLineNo">122</span>   */<a name="line.122"></a>
<span class="sourceLineNo">123</span>  public static Builder&lt;Comparable&gt; expectedSize(int expectedSize) {<a name="line.123"></a>
<span class="sourceLineNo">124</span>    return new Builder&lt;Comparable&gt;(Ordering.natural())<a name="line.124"></a>
<span class="sourceLineNo">125</span>        .expectedSize(expectedSize);<a name="line.125"></a>
<span class="sourceLineNo">126</span>  }<a name="line.126"></a>
<span class="sourceLineNo">127</span><a name="line.127"></a>
<span class="sourceLineNo">128</span>  /**<a name="line.128"></a>
<span class="sourceLineNo">129</span>   * Creates and returns a new builder, configured to build {@code<a name="line.129"></a>
<span class="sourceLineNo">130</span>   * MinMaxPriorityQueue} instances that are limited to {@code maximumSize}<a name="line.130"></a>
<span class="sourceLineNo">131</span>   * elements. Each time a queue grows beyond this bound, it immediately<a name="line.131"></a>
<span class="sourceLineNo">132</span>   * removes its greatest element (according to its comparator), which might be<a name="line.132"></a>
<span class="sourceLineNo">133</span>   * the element that was just added.<a name="line.133"></a>
<span class="sourceLineNo">134</span>   */<a name="line.134"></a>
<span class="sourceLineNo">135</span>  public static Builder&lt;Comparable&gt; maximumSize(int maximumSize) {<a name="line.135"></a>
<span class="sourceLineNo">136</span>    return new Builder&lt;Comparable&gt;(Ordering.natural())<a name="line.136"></a>
<span class="sourceLineNo">137</span>        .maximumSize(maximumSize);<a name="line.137"></a>
<span class="sourceLineNo">138</span>  }<a name="line.138"></a>
<span class="sourceLineNo">139</span><a name="line.139"></a>
<span class="sourceLineNo">140</span>  /**<a name="line.140"></a>
<span class="sourceLineNo">141</span>   * The builder class used in creation of min-max priority queues. Instead of<a name="line.141"></a>
<span class="sourceLineNo">142</span>   * constructing one directly, use {@link<a name="line.142"></a>
<span class="sourceLineNo">143</span>   * MinMaxPriorityQueue#orderedBy(Comparator)}, {@link<a name="line.143"></a>
<span class="sourceLineNo">144</span>   * MinMaxPriorityQueue#expectedSize(int)} or {@link<a name="line.144"></a>
<span class="sourceLineNo">145</span>   * MinMaxPriorityQueue#maximumSize(int)}.<a name="line.145"></a>
<span class="sourceLineNo">146</span>   *<a name="line.146"></a>
<span class="sourceLineNo">147</span>   * @param &lt;B&gt; the upper bound on the eventual type that can be produced by<a name="line.147"></a>
<span class="sourceLineNo">148</span>   *     this builder (for example, a {@code Builder&lt;Number&gt;} can produce a<a name="line.148"></a>
<span class="sourceLineNo">149</span>   *     {@code Queue&lt;Number&gt;} or {@code Queue&lt;Integer&gt;} but not a {@code<a name="line.149"></a>
<span class="sourceLineNo">150</span>   *     Queue&lt;Object&gt;}).<a name="line.150"></a>
<span class="sourceLineNo">151</span>   * @since 8.0<a name="line.151"></a>
<span class="sourceLineNo">152</span>   */<a name="line.152"></a>
<span class="sourceLineNo">153</span>  @Beta<a name="line.153"></a>
<span class="sourceLineNo">154</span>  public static final class Builder&lt;B&gt; {<a name="line.154"></a>
<span class="sourceLineNo">155</span>    /*<a name="line.155"></a>
<span class="sourceLineNo">156</span>     * TODO(kevinb): when the dust settles, see if we still need this or can<a name="line.156"></a>
<span class="sourceLineNo">157</span>     * just default to DEFAULT_CAPACITY.<a name="line.157"></a>
<span class="sourceLineNo">158</span>     */<a name="line.158"></a>
<span class="sourceLineNo">159</span>    private static final int UNSET_EXPECTED_SIZE = -1;<a name="line.159"></a>
<span class="sourceLineNo">160</span><a name="line.160"></a>
<span class="sourceLineNo">161</span>    private final Comparator&lt;B&gt; comparator;<a name="line.161"></a>
<span class="sourceLineNo">162</span>    private int expectedSize = UNSET_EXPECTED_SIZE;<a name="line.162"></a>
<span class="sourceLineNo">163</span>    private int maximumSize = Integer.MAX_VALUE;<a name="line.163"></a>
<span class="sourceLineNo">164</span><a name="line.164"></a>
<span class="sourceLineNo">165</span>    private Builder(Comparator&lt;B&gt; comparator) {<a name="line.165"></a>
<span class="sourceLineNo">166</span>      this.comparator = checkNotNull(comparator);<a name="line.166"></a>
<span class="sourceLineNo">167</span>    }<a name="line.167"></a>
<span class="sourceLineNo">168</span><a name="line.168"></a>
<span class="sourceLineNo">169</span>    /**<a name="line.169"></a>
<span class="sourceLineNo">170</span>     * Configures this builder to build min-max priority queues with an initial<a name="line.170"></a>
<span class="sourceLineNo">171</span>     * expected size of {@code expectedSize}.<a name="line.171"></a>
<span class="sourceLineNo">172</span>     */<a name="line.172"></a>
<span class="sourceLineNo">173</span>    public Builder&lt;B&gt; expectedSize(int expectedSize) {<a name="line.173"></a>
<span class="sourceLineNo">174</span>      checkArgument(expectedSize &gt;= 0);<a name="line.174"></a>
<span class="sourceLineNo">175</span>      this.expectedSize = expectedSize;<a name="line.175"></a>
<span class="sourceLineNo">176</span>      return this;<a name="line.176"></a>
<span class="sourceLineNo">177</span>    }<a name="line.177"></a>
<span class="sourceLineNo">178</span><a name="line.178"></a>
<span class="sourceLineNo">179</span>    /**<a name="line.179"></a>
<span class="sourceLineNo">180</span>     * Configures this builder to build {@code MinMaxPriorityQueue} instances<a name="line.180"></a>
<span class="sourceLineNo">181</span>     * that are limited to {@code maximumSize} elements. Each time a queue grows<a name="line.181"></a>
<span class="sourceLineNo">182</span>     * beyond this bound, it immediately removes its greatest element (according<a name="line.182"></a>
<span class="sourceLineNo">183</span>     * to its comparator), which might be the element that was just added.<a name="line.183"></a>
<span class="sourceLineNo">184</span>     */<a name="line.184"></a>
<span class="sourceLineNo">185</span>    public Builder&lt;B&gt; maximumSize(int maximumSize) {<a name="line.185"></a>
<span class="sourceLineNo">186</span>      checkArgument(maximumSize &gt; 0);<a name="line.186"></a>
<span class="sourceLineNo">187</span>      this.maximumSize = maximumSize;<a name="line.187"></a>
<span class="sourceLineNo">188</span>      return this;<a name="line.188"></a>
<span class="sourceLineNo">189</span>    }<a name="line.189"></a>
<span class="sourceLineNo">190</span><a name="line.190"></a>
<span class="sourceLineNo">191</span>    /**<a name="line.191"></a>
<span class="sourceLineNo">192</span>     * Builds a new min-max priority queue using the previously specified<a name="line.192"></a>
<span class="sourceLineNo">193</span>     * options, and having no initial contents.<a name="line.193"></a>
<span class="sourceLineNo">194</span>     */<a name="line.194"></a>
<span class="sourceLineNo">195</span>    public &lt;T extends B&gt; MinMaxPriorityQueue&lt;T&gt; create() {<a name="line.195"></a>
<span class="sourceLineNo">196</span>      return create(Collections.&lt;T&gt;emptySet());<a name="line.196"></a>
<span class="sourceLineNo">197</span>    }<a name="line.197"></a>
<span class="sourceLineNo">198</span><a name="line.198"></a>
<span class="sourceLineNo">199</span>    /**<a name="line.199"></a>
<span class="sourceLineNo">200</span>     * Builds a new min-max priority queue using the previously specified<a name="line.200"></a>
<span class="sourceLineNo">201</span>     * options, and having the given initial elements.<a name="line.201"></a>
<span class="sourceLineNo">202</span>     */<a name="line.202"></a>
<span class="sourceLineNo">203</span>    public &lt;T extends B&gt; MinMaxPriorityQueue&lt;T&gt; create(<a name="line.203"></a>
<span class="sourceLineNo">204</span>        Iterable&lt;? extends T&gt; initialContents) {<a name="line.204"></a>
<span class="sourceLineNo">205</span>      MinMaxPriorityQueue&lt;T&gt; queue = new MinMaxPriorityQueue&lt;T&gt;(<a name="line.205"></a>
<span class="sourceLineNo">206</span>          this, initialQueueSize(expectedSize, maximumSize, initialContents));<a name="line.206"></a>
<span class="sourceLineNo">207</span>      for (T element : initialContents) {<a name="line.207"></a>
<span class="sourceLineNo">208</span>        queue.offer(element);<a name="line.208"></a>
<span class="sourceLineNo">209</span>      }<a name="line.209"></a>
<span class="sourceLineNo">210</span>      return queue;<a name="line.210"></a>
<span class="sourceLineNo">211</span>    }<a name="line.211"></a>
<span class="sourceLineNo">212</span><a name="line.212"></a>
<span class="sourceLineNo">213</span>    @SuppressWarnings("unchecked") // safe "contravariant cast"<a name="line.213"></a>
<span class="sourceLineNo">214</span>    private &lt;T extends B&gt; Ordering&lt;T&gt; ordering() {<a name="line.214"></a>
<span class="sourceLineNo">215</span>      return Ordering.from((Comparator&lt;T&gt;) comparator);<a name="line.215"></a>
<span class="sourceLineNo">216</span>    }<a name="line.216"></a>
<span class="sourceLineNo">217</span>  }<a name="line.217"></a>
<span class="sourceLineNo">218</span><a name="line.218"></a>
<span class="sourceLineNo">219</span>  private final Heap minHeap;<a name="line.219"></a>
<span class="sourceLineNo">220</span>  private final Heap maxHeap;<a name="line.220"></a>
<span class="sourceLineNo">221</span>  @VisibleForTesting final int maximumSize;<a name="line.221"></a>
<span class="sourceLineNo">222</span>  private Object[] queue;<a name="line.222"></a>
<span class="sourceLineNo">223</span>  private int size;<a name="line.223"></a>
<span class="sourceLineNo">224</span>  private int modCount;<a name="line.224"></a>
<span class="sourceLineNo">225</span><a name="line.225"></a>
<span class="sourceLineNo">226</span>  private MinMaxPriorityQueue(Builder&lt;? super E&gt; builder, int queueSize) {<a name="line.226"></a>
<span class="sourceLineNo">227</span>    Ordering&lt;E&gt; ordering = builder.ordering();<a name="line.227"></a>
<span class="sourceLineNo">228</span>    this.minHeap = new Heap(ordering);<a name="line.228"></a>
<span class="sourceLineNo">229</span>    this.maxHeap = new Heap(ordering.reverse());<a name="line.229"></a>
<span class="sourceLineNo">230</span>    minHeap.otherHeap = maxHeap;<a name="line.230"></a>
<span class="sourceLineNo">231</span>    maxHeap.otherHeap = minHeap;<a name="line.231"></a>
<span class="sourceLineNo">232</span><a name="line.232"></a>
<span class="sourceLineNo">233</span>    this.maximumSize = builder.maximumSize;<a name="line.233"></a>
<span class="sourceLineNo">234</span>    // TODO(kevinb): pad?<a name="line.234"></a>
<span class="sourceLineNo">235</span>    this.queue = new Object[queueSize];<a name="line.235"></a>
<span class="sourceLineNo">236</span>  }<a name="line.236"></a>
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<span class="sourceLineNo">469</span>   *<a name="line.469"></a>
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<span class="sourceLineNo">482</span>   * Each instance of MinMaxPriortyQueue encapsulates two instances of Heap:<a name="line.482"></a>
<span class="sourceLineNo">483</span>   * a min-heap and a max-heap. Conceptually, these might each have their own<a name="line.483"></a>
<span class="sourceLineNo">484</span>   * array for storage, but for efficiency's sake they are stored interleaved on<a name="line.484"></a>
<span class="sourceLineNo">485</span>   * alternate heap levels in the same array (MMPQ.queue).<a name="line.485"></a>
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<span class="sourceLineNo">743</span>   *<a name="line.743"></a>
<span class="sourceLineNo">744</span>   * If the underlying queue is modified during iteration an exception will be<a name="line.744"></a>
<span class="sourceLineNo">745</span>   * thrown.<a name="line.745"></a>
<span class="sourceLineNo">746</span>   */<a name="line.746"></a>
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<span class="sourceLineNo">748</span>    private int cursor = -1;<a name="line.748"></a>
<span class="sourceLineNo">749</span>    private int expectedModCount = modCount;<a name="line.749"></a>
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<span class="sourceLineNo">752</span>    private E lastFromForgetMeNot;<a name="line.752"></a>
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<span class="sourceLineNo">760</span><a name="line.760"></a>
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<span class="sourceLineNo">831</span>     * Returns the index of the first element after {@code c} that is not in<a name="line.831"></a>
<span class="sourceLineNo">832</span>     * {@code skipMe} and returns {@code size()} if there is no such element.<a name="line.832"></a>
<span class="sourceLineNo">833</span>     */<a name="line.833"></a>
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<span class="sourceLineNo">843</span><a name="line.843"></a>
<span class="sourceLineNo">844</span>  /**<a name="line.844"></a>
<span class="sourceLineNo">845</span>   * Returns an iterator over the elements contained in this collection,<a name="line.845"></a>
<span class="sourceLineNo">846</span>   * &lt;i&gt;in no particular order&lt;/i&gt;.<a name="line.846"></a>
<span class="sourceLineNo">847</span>   *<a name="line.847"></a>
<span class="sourceLineNo">848</span>   * &lt;p&gt;The iterator is &lt;i&gt;fail-fast&lt;/i&gt;: If the MinMaxPriorityQueue is modified<a name="line.848"></a>
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<span class="sourceLineNo">850</span>   * iterator's own remove method, the iterator will generally throw a<a name="line.850"></a>
<span class="sourceLineNo">851</span>   * {@link ConcurrentModificationException}. Thus, in the face of concurrent<a name="line.851"></a>
<span class="sourceLineNo">852</span>   * modification, the iterator fails quickly and cleanly, rather than risking<a name="line.852"></a>
<span class="sourceLineNo">853</span>   * arbitrary, non-deterministic behavior at an undetermined time in the<a name="line.853"></a>
<span class="sourceLineNo">854</span>   * future.<a name="line.854"></a>
<span class="sourceLineNo">855</span>   *<a name="line.855"></a>
<span class="sourceLineNo">856</span>   * &lt;p&gt;Note that the fail-fast behavior of an iterator cannot be guaranteed<a name="line.856"></a>
<span class="sourceLineNo">857</span>   * as it is, generally speaking, impossible to make any hard guarantees in the<a name="line.857"></a>
<span class="sourceLineNo">858</span>   * presence of unsynchronized concurrent modification.  Fail-fast iterators<a name="line.858"></a>
<span class="sourceLineNo">859</span>   * throw {@code ConcurrentModificationException} on a best-effort basis.<a name="line.859"></a>
<span class="sourceLineNo">860</span>   * Therefore, it would be wrong to write a program that depended on this<a name="line.860"></a>
<span class="sourceLineNo">861</span>   * exception for its correctness: &lt;i&gt;the fail-fast behavior of iterators<a name="line.861"></a>
<span class="sourceLineNo">862</span>   * should be used only to detect bugs.&lt;/i&gt;<a name="line.862"></a>
<span class="sourceLineNo">863</span>   *<a name="line.863"></a>
<span class="sourceLineNo">864</span>   * @return an iterator over the elements contained in this collection<a name="line.864"></a>
<span class="sourceLineNo">865</span>   */<a name="line.865"></a>
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<span class="sourceLineNo">883</span>  /**<a name="line.883"></a>
<span class="sourceLineNo">884</span>   * Returns the comparator used to order the elements in this queue. Obeys the<a name="line.884"></a>
<span class="sourceLineNo">885</span>   * general contract of {@link PriorityQueue#comparator}, but returns {@link<a name="line.885"></a>
<span class="sourceLineNo">886</span>   * Ordering#natural} instead of {@code null} to indicate natural ordering.<a name="line.886"></a>
<span class="sourceLineNo">887</span>   */<a name="line.887"></a>
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<span class="sourceLineNo">891</span><a name="line.891"></a>
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<span class="sourceLineNo">893</span>    return queue.length;<a name="line.893"></a>
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<span class="sourceLineNo">896</span>  // Size/capacity-related methods<a name="line.896"></a>
<span class="sourceLineNo">897</span><a name="line.897"></a>
<span class="sourceLineNo">898</span>  private static final int DEFAULT_CAPACITY = 11;<a name="line.898"></a>
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<span class="sourceLineNo">900</span>  @VisibleForTesting static int initialQueueSize(int configuredExpectedSize,<a name="line.900"></a>
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<span class="sourceLineNo">906</span><a name="line.906"></a>
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<span class="sourceLineNo">917</span>  private void growIfNeeded() {<a name="line.917"></a>
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<span class="sourceLineNo">921</span>      System.arraycopy(queue, 0, newQueue, 0, queue.length);<a name="line.921"></a>
<span class="sourceLineNo">922</span>      queue = newQueue;<a name="line.922"></a>
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<span class="sourceLineNo">925</span><a name="line.925"></a>
<span class="sourceLineNo">926</span>  /** Returns ~2x the old capacity if small; ~1.5x otherwise. */<a name="line.926"></a>
<span class="sourceLineNo">927</span>  private int calculateNewCapacity() {<a name="line.927"></a>
<span class="sourceLineNo">928</span>    int oldCapacity = queue.length;<a name="line.928"></a>
<span class="sourceLineNo">929</span>    int newCapacity = (oldCapacity &lt; 64)<a name="line.929"></a>
<span class="sourceLineNo">930</span>        ? (oldCapacity + 1) * 2<a name="line.930"></a>
<span class="sourceLineNo">931</span>        : IntMath.checkedMultiply(oldCapacity / 2, 3);<a name="line.931"></a>
<span class="sourceLineNo">932</span>    return capAtMaximumSize(newCapacity, maximumSize);<a name="line.932"></a>
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<span class="sourceLineNo">935</span>  /** There's no reason for the queueSize to ever be more than maxSize + 1 */<a name="line.935"></a>
<span class="sourceLineNo">936</span>  private static int capAtMaximumSize(int queueSize, int maximumSize) {<a name="line.936"></a>
<span class="sourceLineNo">937</span>    return Math.min(queueSize - 1, maximumSize) + 1; // don't overflow<a name="line.937"></a>
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<span class="sourceLineNo">939</span>}<a name="line.939"></a>




























































</pre>
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